Lab: Building Container Images

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• Launch the lab
• What you'll learn
• Modules

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Take a working but naïve Dockerfile and progressively improve it into a production-grade image. Each section introduces one technique, applied to a real Python Flask app, so you can see the impact directly.

Launch the lab

{{< labspace-launch image="dockersamples/labspace-building-images" >}}

What you'll learn

By the end of this Labspace, you will have completed the following:

• Read an image's layer history and understand the layer cleanup pitfall
• Restructure a Dockerfile for fast, cache-efficient incremental builds
• Write a .dockerignore file and run containers as a non-root user
• Use multi-stage builds to run tests as a build gate and dramatically reduce image size
• Choose the right base image for production, including Docker Hardened Images
• Inject secrets safely at build time using --mount=type=secret

Modules

#	Module	Description
1	Welcome & Your First Build	Explore the sample app and build the initial image
2	Understanding Image Layers	Inspect layers with docker history and see the layer cleanup pitfall
3	Dockerfile Best Practices	Fix cache ordering, add .dockerignore, and switch to a non-root user
4	Multi-Stage Builds	Run tests as a build gate and use a slim base for the production stage
5	Choosing a Base Image	Compare slim, Alpine, and Docker Hardened Images
6	Build Secrets	Show why ARG leaks secrets and use --mount=type=secret safely
7	Wrap-up	Review the complete best-practices checklist and next steps